1. Field of the Invention
The present invention relates to a method for producing 1,4-bis(dichloromethyl)tetrafluorobenzene (DCMTFB) and, more particularly, to a method for producing high-yield 1,4-bis(dichloromethyl)tetrafluorobenzene in mass production.
2. Description of Related Art
Parylene polymers possess numerous advantages for manufacturing purposes. For example, the coating environment is at room temperature; no residual stress exists after coating; and precise controls are allowed on the thickness of the deposition film. Additionally, parylene polymer films have advantages such as uniformity, excellent acid and alkali resistance, high transparency and low dielectric constant. Therefore, they have been widely employed in electric insulation on printing circuit boards, damp-proofing on sensors or medical instruments, and anti-corrosion on metal-coating, etc. Presently, the fluoro parylene polymers, for their low dielectric constant and high melting point, can be utilized on dielectric coating in the electrical and coating industries and have become the focus of the attention.
One of fluoro parylene polymers, for example, poly(tetrafluoro-p-xylene) has the structure represented by the following Formula (1).
Fluoro parylene polymers are generally coated on products by means of chemical vapor deposition in a vacuum at room temperature. Products coated with fluoro parylene polymers not only possess excellent anticorrosive, damp-proofing and insulating characteristics, but also have the advantages of extra thinness, transparency and being poreless. By polymerizing active monomers on the object surfaces, fluoro parylene polymer coatings can be formed. Unlike the general steps of liquid coating process, there is another coating process to have the parylene dimers vaporized first, and as the dimer bonds are cleaved to yield monomer free radicals at a pyrolysis condition, the monomer free radicals are polymerized to form parylene polymers.
Currently, the dimer of fluoro parylene polymers often used in the industry is octafluoro-2,2-paracyclophane represented by the following Formula (2).

The dielectric constant of fluoro parylene polymers decreases as the number of fluorine atoms increases within the polymers. Thus, it can be predicted that the parylene polymers polymerized from the dimer of fluoro parylene polymers, represented by the following Formula (3) and containing no hydrogen atoms, can have a lower dielectric constant.

It is important for 1,4-bis(bromodifluoromethyl)tetrafluorobenzene (BFTFB) represented by the following Formula (4) to be the monomer of the above-mentioned dimer, to not contain any hydrogen atoms, of fluoro parylene polymers.

1,4-bis(dichloromethyl)tetrafluorobenzene (DCMTFB), as shown in the following Formula (5), is a critical precursor for synthesis of the foregoing 1,4-bis(bromodifluoromethyl)tetrafluorobenzene (BFTFB).

Nowadays, 1,4-bis(dichloromethyl)tetrafluorobenzene (DCMTFB) is synthesized by reacting 1,2,4,5-tetrafluorobenzene (TFB) with CHCl3, as shown in the following Reaction (I).
However, this method is time-consuming and low-yielding, and needs silica-gel column chromatography to purify the crude product. Hence, this method is unsuitable for mass production.
Therefore, it is desirable to provide a prompt and high-yield method for synthesize 1,4-bis(dichloromethyl)tetrafluorobenzene (DCMTFB), and such method is appropriate for mass production.